Flexible ebonite

Flexible Ebonite This can be called semi-ebonite usually loaded with mineral fillers with a lower proportion of sulphur, say 15 phr, and by incorporating into the compound synthetic rubbers like polychloroprene, polyisobutylene or butyl rubber. This ebonite will have good resistance to impact. A sheet made of flexible ebonite will look like a hard flexible leather. 

These filters were used in illmenite beneficiation and titanium dioxide plants. These and their parts like agitators, troughs etc., were lined with a semi-hard flexible ebonite of natural rubber to protect the equipment against the abrasive action of the ore and solid particles in the slurries. 

There is yet another type of lining called the Triflex lining. Triflex is a three ply, soft-hard-soft natural rubber construction. The soft rubber is compounded for maximum rubber to metal adhesion. The middle hard rubber layer, a flexible ebonite composition,... 

A form of cellular rubber in which the cells are non-intercommunicating, self-contained units. It has low thermal conductivity. Expanded rubber is buoyant and does not absorb water and was therefore initially used in both the soft rubber and ebonite forms in the construction of lifebuoys and other marine buoyancy equipment. The most commonly used polymer is now polyurethane for both flexible and rigid systems. 

However, for construction purposes, solid ebonites were chosen. As is known from rubber chemistry, solid ebonite, commonly known as hard rubber, is a polymer material with sulfur content used for vulcanization. Ebonite, like elastomeric or flexible rubber, is made from a combination of sulfur with polydienes (unsaturated rubbers containing double bonds). The sulfur and polydienes are combined with some auxiliary additives and heated to produce vulcanization. Typical mass ratios of sulfur to rubber are 2 100 for elastomeric rubber and 40 100 for hard rubber. Due to the large degree of sulfide cross linking formed in the vulcanization process, solid ebonite is a hard, non-flexible, plastic-like material possessed of... 

Vulcanized rubber can be carved, or, more importantly, molded into almost any shape. The uses for this versatile, water-proof, flexible material increased with time. These included household and decorative objects, apparel, personal items, insulation, and equipment and materials for use in medicine, the military, and industry. Vulcanized rubber also goes under the commercial names vulcanite and ebonite. 

The electrolyser consists of a rectangular trough with a cover on top connected at both ends to the end boxes. The box at the mercury inlet is called the inlet box, and the other is the outlet box. The trough is of mild steel construction with ebonite lined bottom and sides. The covers are of mild steel construction with ebonite lining on the inside surface or only of rubber sheets called flexible cell covers. The covers have holes for fixing anodes. 

Figure 12). Some materials can have only a few crosslinks, such as permanent press materials where the fabric contour is locked into place with crosslinks. Otliers materials such as Bakelite and ebonite are heavily crosshnked tliese are hard, brittle, non-flexible materials. 

Poisson s ratio is a measure of the reduction in the cross section accompanying stretching and is the ratio of the transverse strain (a contraction for tensile stress) to longitudinal strain (elongation). Poisson s ratio for many of the more brittle plastics such as polystyrene, the acrylics, and the thermoset materials is about 0.3 for the more flexible plasticized materials, such as cellulose acetate, the value is somewhat higher, about 0.45. Poisson s ratio for rubber is 0.5 (characteristic of a liquid) it decrease to 0.4 for vulcanized rubber and to about 0.3 for ebonite. Poisson s ratio varies not only with the nature of the material but also with the magnitude of the strain for a given material. All values cited here are for zero strain. 

Soft rubber is used for cable insulation, flexible hose, shock ab> sorbers, as a gasket material, and as a lining for iron and steel vessels and pipelines. When used as a lining, rubber is applied to the vessel with a special adhesive. Hard ebonites may be used for pump or valve linings and, without metal support, for smaller vessels. 

Cross-linking reduces chain flexibility and-hence raises the Tg. The best known apparent demonstration of this is the fact that when natural rubber is reacted with large amounts of sulphur the product, ebonite, is a rigid material. In fact ebonite is not a particularly good example since in addition to network formation there is also a considerable amount of intramolecular reaction. Nevertheless the following data (Ueberreiter and Jenckel, 1939) in Table 4.3 shows a steady increase of Tg with combined sulphur. 

One of the recent contributions to rubber technology has been the development of methods whereby both natural and synthetic, both cured and uncured, may be bonded directly to metal surfaces. Earliest methods used to fasten rubber to metal were mechanical. Ebonite was also used in early work, the ebonite surface giving a strong adhesion to the metal while uniting with the rubber on the other side. Ebonite as a bonding agent reduces the flexibility of the unit as a whole, especially when the rubber section itself is not very thick. Secondly, ebonite is thermoplastic and the tenacity of the bond falls off rapidly even at moderate temperature. Recently, other modified derivatives of rubber have become avail-... 

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